Method and Device for Producing a Composite Yarn

ABSTRACT

The invention concerns a method for making continuous coextruded intermingled glass filaments and continuous thermoplastic organic filaments that enable non-spinnable compounds to be incorporated at the thermoplastic filaments. The invention is characterized in that the thermoplastic filaments are obtained by coextrusion of a thermoplastic material acting as core and a thermoplastic material containing at least one non-spinnable compound. The invention also concerns a device for implementing the method. The resulting composite yarn is provided with specific core properties provided by the non-spinnable compounds.

The invention relates to a process and to a device for manufacturing acomposite strand formed by combining a plurality of continuous glassfilaments intermingled with continuous organic thermoplastic filaments.

Processes for producing a composite strand comprising such glassfilaments and an organic thermoplastic are already known.

EP-A-0 367 661 describes a process employing a first installationcomprising a bushing that contains molten glass, from which continuousglass filaments are attenuated, and a second installation comprising aspinning head, supplied under pressure with an organic thermoplasticthat delivers continuous filaments. During assembly, the two types offilaments may be in the form of webs, or in the form of a web and astrand.

This process allows a composite strand to be obtained in which thethermoplastic filaments surround the glass filaments, which are thusprotected from the effects of abrasion due to rubbing on the members forguiding, assembling and collecting said strand.

EP-A-0 505 275 proposes a process for manufacturing a composite strandsimilar to that described above in EP-A-0 367 661, which uses at leastone spinning head normally used in the industrial field of syntheticfibers.

This document recommends drawing the organic filaments into one or morewebs defining, partly or completely, a region or conical or pyramidalshape comprising an open sector via which the glass strand isintroduced.

Document EP-A-0 599 695 describes the manufacture of a composite strandconsisting of commingled glass filaments and thermoplastic filamentswhich consists in combining a bundle or web of continuous glassfilaments emanating from a bushing with a web of continuousthermoplastic filaments produced from a spinning head, saidthermoplastic filaments having, during their penetration into the glassweb or bundle, a drawing speed greater than the speed of the glassfilaments.

The improvement consists here in overdrawing the thermoplastic filamentsin order to compensate for their shrinkage, thereby making it possibleto obtain a composite strand exhibiting no waviness during its formationand being stable over time.

EP-A-0 616 055 also proposes a process for producing aglass/thermoplastic composite strand by commingling a web ofthermoplastic filaments with a bundle or web of glass filaments, inwhich the thermoplastic filaments upstream of the point of convergenceare heated to a temperature above their relaxation temperature drawn andthen cooled.

Finally, WO-A-02/31231 describes the manufacture of aglass/thermoplastic composite strand of high linear density. Accordingto that process, the glass filaments and the thermoplastic filaments aredivided into several webs, at least one thermoplastic web is mingledwith each glass web and the filaments are gathered together into atleast one composite strand. This process helps to improve thecommingling of the filaments.

The composite strand obtained by the processes that have just beendescribed has the desired properties for producing composite productswith a fiber-reinforced thermoplastic matrix. In particular, itsmechanical properties have a satisfactory level of performance, which isassessed by the good quality of the bonding between the thermoplasticmatrix and the material that reinforces it.

However, certain applications require the composite product to beprovided with additional properties, for example the ability to be fireresistant and/or resistant to ultraviolet and/or heat, the possibilityof being colored and the capability of conducting electrical current.

Conventionally the intended properties are obtained by treating thecomposite strand or assemblies of these strands (meshes, mats, wovens,knits, braids) with appropriate compounds, such as fire retardants,antioxidants and thermal stabilizers, dyes, and conductive fillers inorder to fulfill the aforementioned functions. The way in which thetreatment is carried out is known and this may especially be powdercoating, spraying, immersion in a bath of liquid material (solution,dispersion or emulsion) or molten material, or coating. The treatmentsare generally carried out by the final user and require particularlyexpensive and bulky installations that generate problems (dust,moisture, etc.), which have, among other drawbacks, that of being ableto treat only the surface of the strand.

Now, it proves to be beneficial to be able to treat the composite strand“right to the core” by incorporating compounds capable of fulfilling theaforementioned functions within the constituent filaments of the strand,more particularly on or in the thermoplastic material in the filamentarystate.

This task is made difficult by the fact that said compounds are notusually “spinnable” and that, as a consequence, they cannot beintroduced in the form of filaments into the composite strand.

Furthermore, usually said compounds are chemically incompatible orbarely compatible with the thermoplastic of the filaments. Now, it isknown that in general the deposition of such compounds on filaments inthe course of formation or their introduction into the thermoplasticbefore spinning, for example into the extruder that feeds the spinninghead, upsets the spinning operation or even makes it impossible.

Moreover, the quality of the spinning of the thermoplastic filamentsmust be as constant as possible, especially as regards the diameter ofthe filaments, given that these have to be combined with the glassfilaments and that consequently this combining operation must notdisturb the fiberizing of the glass either.

The subject of the present invention is a process for manufacturing acomposite strand that makes it possible to incorporate nonspinablecompounds in the filamentary stage and to provide the composite strandwith specific properties “right to the core”.

The problem posed by introducing nonspinable compounds into thecomposite strand is solved by a process for manufacturing a compositestrand formed by combining continuous glass filaments emanating from atleast one bushing with continuous thermoplastic filaments emanating fromat least one spinning head, these filaments being drawn and commingledin the form of a web into a bundle or web of glass filaments, in whichthe thermoplastic filaments are obtained by coextruding a main organicthermoplastic with a secondary organic thermoplastic containing at leastone nonspinable compound.

The term “nonspinable compound” is understood here to mean a compoundthat is not capable of giving filaments under the conventionalconditions of extrusion-spinning processes.

The term “main organic thermoplastic” is understood to mean the organicthermoplastic present in a major amount, which constitutes as it werethe core of the thermoplastic filaments and serves as support for thenonspinable compound(s) blended with the thermoplastic present in aminor amount, as will be explained below. For the sake ofsimplification, the main organic thermoplastic will be called hereafter“main material”.

The term “secondary organic thermoplastic” is understood to mean theblend of the organic thermoplastic present in a minor amount with atleast one nonspinable compound as such. The secondary organicthermoplastic will be denoted hereafter by “secondary material”.

The coextrusion allows the secondary material in melt form to beincorporated into the main material, also in melt form, and betransported by the core filaments when they are drawn.

According to a first preferred embodiment, the coextrusion is carriedout under conditions such that the secondary material is distributedover all or part of the surface of the main material serving as core.The secondary material may be uniformly distributed or randomlydistributed on the main material, and it may take the form, for example,of a continuous or discontinuous coating, or of clumps (platelets,droplets etc.). The form that the secondary material can adopt is notcritical, the essential point being that it is capable of serving as acarrier for the nonspinable compound(s). The nonspinable compound(s)especially when in the form of particles, may be entirely included inthe secondary material or partly therein, the other part being in themain material and/or being free on the surface.

According to another embodiment, the coextrusion is carried out underconditions such that the secondary material is included in the mainmaterial. The distribution of the secondary material within eachthermoplastic filament depends on the spinning head used, as will beexplained later. This procedure makes it possible to introduce thenonspinable compound(s) into the thermoplastic filament. However, thespinning under these conditions is more tricky than previously. Becauseof the imperfect extrusion of the secondary material, due to thepresence of nonspinable compound(s), the filaments have a diameter thatvaries over the course of time, giving in the end a strand having a moreirregular linear density.

The coextrusion makes it possible to introduce compounds that areintrinsically nonspinable onto or into the thermoplastic filaments.After the thermoplastic filaments thus produced have been combined withthe glass filaments, the composite strand has “right to the core”specific functions that depend on the nature of the nonspinablecompounds that it contains.

The organic thermoplastics of the main material and of the secondarymaterial must be, at least partly, chemically compatible so as to avoidproblems of delamination of these materials.

The main material is chosen from polyolefins such as polyethylene andpolypropylene, polyesters such as polyethylene terephthalate andpolybutylene terephthalate, polyamides such as nylon-6, nylon-6,6 andnylon-12, polyphenylene sulfide and polyurethanes. Preferably,polypropylene is used.

The organic thermoplastic of the secondary material may be chosen fromthe organic thermoplastics mentioned in the case of the main material inthe previous paragraph. It may be of the same or different nature.Preferably, the main and secondary materials are of the same nature.

The nonspinable compounds may be:

-   -   thermally or electrically conductive fillers, for example metal        or graphite particles;    -   mineral fillers capable of reducing the shrinkage and increasing        the hardness of the composites, for example in the form of        particles of calcium carbonate, calcium magnesium carbonate,        silica, clays, especially containing silicates such as        aluminosilicates, in particular in the form of lamellar        nanofillers, and barium sulfate;    -   fire retardants, for example halogen compounds or compounds not        combined with antimony oxide, and phosphates;    -   coloring agents, for example carbon black;    -   adhesive agents, for example hot-melt adhesive polymers; and    -   UV stabilizers, for example sterically hindered amines, or        thermal stabilizers, for example phenolic compounds and        phosphites.

The amount of main material represents at least 50%, preferably 70 to95%, of the total weight of the thermoplastic filaments the balance to100% being represented by the secondary material.

The weight content of nonspinable compound(s) in the secondary materialis less than 80%, preferably varying from 1 to 50% and better stillvarying from 10 to 30%.

In the strand, the content of nonspinable compound(s) varies dependingon the chemical nature and the properties to be conferred on thecomposite strand and to be given to the final composite obtained fromthis strand. In general, the amount of nonspinable compound(s)represents 0.1 to 30% preferably 0.5 to 15% by weight of thethermoplastic. Above 30%, the spinability is greatly reduced, with ahigh risk of breaking the thermoplastic filaments or breaking the glassfilaments during the combining with thermoplastic filaments havingsubstantial irregularities, for example in terms of the diameter or thedistribution of the nonspinable compound(s).

Thanks to the invention, the nonspinable compounds are included in thecomposite strand in the filamentary stage and are not distributed juston the surface of the strand as is known hitherto. The nonspinablecompounds may be incorporated into the composite strand in a largeamount without the spinning of the thermoplastic filaments beingdisturbed thereby.

Another advantage of the process is that it allows one or morenonspinable compounds to be deposited in a constant amount by precisecontrol of the output, which is difficult to achieve with certaintreatments such as powder coating and other coating treatments.

Yet another advantage of the process is that it can be modulated and itallows the nonspinable compound(s) to be changed in a very short timesince only one feed for said compound(s) is needed per spinning head.Consequently, it is easy to purge the device and make it operate with anew blend of the same secondary material or with another one, with oneor more other nonspinable compounds. In the event of an incident, therestart operation in the spinning head is also easier.

The invention also proposes a device for implementing this process.

According to the invention, to manufacture the composite strand formedfrom continuous glass filaments and continuous organic thermoplasticfilaments, this device comprises, on the one hand, an installationcomprising at least one bushing supplied with molten glass, the lowerface of which has a very large number of holes, this bushing beingcombined with a coater, and, on the other hand, an installationcomprising at least one spinning head suitable for coextrusion andsupplied under pressure with the main material in melt form and with thesecondary material also in melt form, this spinning head having a verylarge number of holes and being combined with means for drawing andspraying said filaments for the purpose of mingling them with the glassfilaments, and finally means common to the two installations forassembling and optionally winding at least one composite strand.

When the strand is not collected in the form of a wound package, thedevice includes a moving receiving support, for example a conveyor belt,onto which the strand, following assembly of the filaments, is directlyprojected so as to form a continuous strand mat.

The device may further include a chopper that cuts up the strand beforeit is projected onto the receiving support, in order to form a choppedstrand mat or granules that can be used for example to produceinjection-molded or compression-molded parts.

The bushing supplied with molten glass preferably has 400 to 8000 holesfrom which the glass filaments are attenuated.

The spinning head may be chosen from known spinning heads, in particularthose known for producing multicomponent textile strands. Preferably,the spinning head has 400 to 8000 holes from which the main andsecondary materials are coextruded.

Combined with the spinning head are two extruders used for supplyingmolten organic thermoplastics, one for the main material and the otherfor the secondary material.

The spinning head includes a spinneret plate provided with a very largenumber of holes preferably distributed in the form of a ring or of aseries of concentric rings from which the main material and thesecondary material are coextruded in order to form filaments that aredrawn before being commingled with the glass filaments.

Preferably, the spinning head has an internal geometry allowing the mainmaterial and the secondary material to be delivered separately right tothe spinneret plate. The spinning head is thus suitable for distributingthe materials in such a way that the main material flows as thepredominant stream of all the extruded materials and serves as a carrierfor catching and transporting the secondary material that contains thenonspinable compound(s).

The flow rates of the materials are controlled so that the stream of themain material represents at least 50%, preferably 70 to 95%, by weightof all of the materials entering the spinning head.

The spinning heads according to the invention make it possible to obtainfilaments in which either the secondary material lies on the peripheryand the main material occupies the center, for example of the orangesegment type (FIG. 3 a) or of the core-sheath type (FIGS. 3 b and c), orthe two materials are juxtaposed for example of the side-by-side type(FIG. 3 d) or else the secondary material is included within the mainmaterial, for example of the “islands in a sea” type (FIG. 3 e).

Spinning heads that allow the secondary material to be distributedaround the periphery of the main material or that allow the main andsecondary materials to be juxtaposed are preferred.

The means for drawing the thermoplastic filaments may for example be adrawing unit of the type comprising drums, which is described inWO-A-98/01751 or EP-A-0 599 695. The thermoplastic filaments are drawnprior to being and commingled with the glass filaments, which makes itpossible to limit their shrinkage and to prevent waviness in thecomposite strand. Such a strand proves to be advantageous for producingcross-wound packages.

Advantageously, the drawing unit is of the type described in EP-A-0 616055. It comprises at least three groups of drums, the first group beingcomposed of heated drums. The second group comprises drums rotated at aspeed higher than that of the preceding drums and the third groupcomprises cooled drums rotated at a speed identical to that of the lastdrum of the second group. The additional heating/cooling step improvesthe stability of the strand over time.

The means for projecting the thermoplastic filaments may be formed bythe combination of two rolls, namely a first guide roll, which serves todirect the web of thermoplastic filaments toward a second roll, wherethe commingling with the glass filaments takes place (see EP-A-0 616055), or this means may consist of a Venturi system.

These means cause intermingling of the glass filaments on the one handand the thermoplastic filaments on the other, these filaments arrivingwith identical speeds. The commingled filaments are thus linear.Preferably, the speed of projection of the thermoplastic filaments intothe glass filaments is of the order of 1000 meters per minute.

In a variant, it is possible to obtain composite strands whose glassfilaments are linear and whose thermoplastic filaments are wavy. Thistype of relatively bulky strand is desirable in certain textileapplications requiring good “covering” power. To do this, all that isrequired is to modify the speed of rotation of the drums of the drawingunit so as to give the thermoplastic filaments a higher speed than thatof the glass filaments before they are commingled.

The devices described make it possible to produce a composite strandconsisting of glass filaments and thermoplastic filaments containingnonspinable material distributed in the strand, either on the surface orwithin the thermoplastic filaments, unlike the strands of the prior artin which said material lies only on the surface of the strand.

Such devices also have the advantages of taking up less room in thespinning heads, of being able to be fitted onto an existing installationusually having several positions for fiberizing the glass, withoutrequiring consequent modifications, and of allowing the spinning headmaintenance and cleaning operations to be carried out without disturbingthe operation of the rest of the manufacturing line.

A further subject of the invention is the composite strand obtainedaccording to the process of the invention.

This strand preferably consists of 400 to 8000 glass filaments and 400to 8000 thermoplastic filaments. The glass filaments may be made of anyknown type of glass, for example AR (alkaline-resistant) glass R-glass,S-glass or E-glass, the latter being preferred.

The linear density of the composite strand is at least equal to 100 texand at most equal to 10 000 tex. Preferably, the linear density is atleast 500 tex and advantageously at least 1500 tex.

This glass/thermoplastic composite strand may be used to produce partsmade of composites consisting of a thermoplastic matrix reinforced byglass strands using the techniques of pultrusion and filament winding.The strand may also be used to produce intermediate products, such asmats, wovens, knits and braids, suitable for vacuum molding, bladdermolding membrane molding and compression molding. If appropriate, theseproducts may undergo a heat treatment for the purpose of partiallymelting the thermoplastic so as to consolidate their structure and allowbetter handling.

Further details and features of the invention will become apparent onreading the detailed description below, illustrated by the followingfigures:

FIG. 1 shows a schematic view of an installation according to theinvention;

FIGS. 2 a-2 c show a longitudinal sectional view of spinning headsaccording to the invention at a coextrusion orifice; and

FIGS. 3 a-3 e show a cross-sectional view of the thermoplastic filamentsobtained according to the invention.

The invention illustrated in FIG. 1 comprises a bushing 1, supplied withmolten glass either from the forehearth of a furnace that feeds theglass directly from its top, or via a hopper containing cold glass, forexample in the form of beads that drop under gravity.

The bushing 1, whatever the type of feed, is generally made of aplatinum-rhodium alloy and is heated by resistance heating so as to keepthe glass at a high temperature or to remelt it, depending on the case.A multitude of streams of molten glass flow from the bushing 1, thesebeing attenuated in the form of a bundle 2 by a device (not shown),which also forms the wound package 3. Placed in the path of the bundle 2is a coating roll 4, for example made of graphite, which deposits on theglass filaments a size composition intended to prevent or limit therubbing of the filaments on the various members with which they comeinto contact. The size may be any known aqueous or anhydrous (containingless than 5% water) size and it may contain compounds which form part ofthe composition of the thermoplastic filaments 5 that will combine withthe glass filaments to form the composite strand 6.

Thermoplastic filaments 5 are extruded from the spinning head 7, whichis shown schematically. The spinning head is fed with the molten mainmaterial coming from the extruder 8 (not shown) fed with granules andwith the secondary material, which is also molten, comprising the blendof a molten organic thermoplastic and a nonspinable compound, output bythe extruder 9 (not shown) fed with granules of organic thermoplasticand of powder of a nonspinable compound.

The main and secondary thermoplastics flow under pressure into thespinneret and are extruded through the very many holes in a spinneretplate into filaments 5 that are immediately drawn. As soon as they areformed, the filaments 5 are cooled by a blowing device 10 supplied witha gaseous fluid. The filaments then pass over a roll 11, which makes itpossible on the one hand, to gather them in the form of a web 12 and, onthe other hand, to deflect their path. The web 12 is then directedtoward the drum drawing unit 13 which here consists of six drums 14, 15,16, 17, 18 and 19.

The drums 14, 15, 16, 17, 18 and 19 have different speeds so that theycreate an acceleration in the run direction of the web 12. Here, thedrums operate in pairs—associated with the drums 14, 15 forming thefirst pair is a heater, for example an electrical heater (not shown),which makes it possible, by contact, to increase the temperature of thethermoplastic filaments uniformly and rapidly. The rise in temperaturedepends on the nature of the thermoplastics used. The drums 14, 15 arerotated at the same speed, which allows the thermoplastic filaments 5 tobe drawn from the spinning head 7.

The second pair of drums 16, 17 is rotated at a higher speed than thatof the first pair. The web 12 of thermoplastic filaments heated bypassing over the first pair of drums 14, 15 undergoes an accelerationdue to the difference in speed of the two pairs of drums, whichacceleration results in an elongation of the filaments of the web 12 andmodifies their structure.

The last pair of drums 18, 19 is rotated at the same speed or a higherspeed than that of the previous pair and includes a cooling device (notshown), for example of the water-jacket type, which allows the structureof the filaments of the web 12 to be set.

The web 12 of thermoplastic filaments is heated and cooled rapidly anduniformly.

The drawing unit 13 may have a larger number of drums, provided thatthey comply with the three aforementioned zones, namely heating, drawingand cooling. Moreover, each of these zones may consist of only a singledrum. The drawing unit may also consist of a succession of groups formedby the three zones that have just been mentioned.

The web 12 of thermoplastic filaments then passes over a deflecting roll20 and through a Venturi system 21 which keeps them as individualthermoplastic filaments and projects them into the sheet of glassfilaments 22 coming from the bundle 2. The device 21 operates by aninjection of compressed air and it imparts no additional speed to theweb 12, thereby limiting the risk of said glass filaments beingdisturbed.

The web 12 of thermoplastic filaments and the web 22 of glass filamentsare joined between the coating roll 4 and the device 23 for assemblingthe composite strand. This arrangement makes it possible to correctlyadapt the geometry of the glass web and to uniformly distribute the twotypes of filaments. A deflector 24 provided with notches keeps thefilaments in place in particular along the edges, and helps to reduceany disturbance suffered by the glass web 22 at the moment when the web12 of thermoplastic filaments is projected into it.

The web 25 of intermingled glass and thermoplastic filaments isassembled by the device 23 into a strand, which strand is immediatelywound up into the package 3 thanks to the winding device (not shown)that operates at a given linear speed kept constant in order toguarantee the desired linear density.

This linear space which allows the glass filaments to be drawn, is inthis case identical to that which the drums 18, 19 impart on the web 12of thermoplastic filaments. In this way, the thermoplastic filamentshave the same speed during the mingling and the composite strand, on itsformation, has no waviness.

FIGS. 2 a-2 c are longitudinal sectional schematic views of the spinninghead illustrated schematically in FIG. 1, at a coextrusion orifice, fordifferent embodiments.

In FIG. 2 a, the molten main material 26 coming from an extruder (notshown) fed via the channel 27 and the secondary material 28, alsomolten, coming from another extruder (not shown) fed via the channel 29converge on the orifice in the spinneret plate 30. Owing to the effectof the pressure, the main and secondary materials are coextruded to formthe filament 31. In this filament, the main material occupies the centerand the secondary material is distributed around the periphery, asindicated in FIG. 3 b.

FIG. 2 b illustrates a second embodiment for obtaining a filament 31 inwhich the main material 26 and the secondary material 28 are distributedas illustrated in FIG. 3 d.

FIG. 2 c illustrates a third embodiment for obtaining a filament 31 inwhich the secondary material 28 is included within the main material 26as shown in FIG. 3 e.

FIG. 3 shows schematically cross sections of preferred thermoplasticfilaments as obtained at the exit of the spinning head.

The main material 26 (shown in black) and the secondary material 28(shown in white) are distributed in various ways in the filament.

In FIGS. 3 a-3 c, the main material occupies the center of the filamentand the secondary material lies around the periphery with a distributionof the orange segment (FIG. 3 a) or coaxial core-sheath (FIG. 3 b) ornoncoaxial core-sheath (FIG. 3 c) type.

In the filaments shown in FIG. 3 d, the main and secondary materials arejuxtaposed in an arrangement of the side-by-side type.

In the filament shown in FIG. 3 e, the secondary material is includedwithin the main material in the “islands in a sea” form.

EXAMPLES

A composite strand was produced in the installation illustrated in FIG.1 that includes the coextrusion spinning head of FIG. 2 a.

The strand consisted of 1600 E-glass filaments 18.5 μm in diameter and1600 thermoplastic filaments obtained by coextruding polypropylene witha polypropylene/carbon black compound. The composite strand contained75% glass, 24.4% polypropylene and 0.6% carbon black by weight. Thestrand had an intense black color allowing composite parts to beproduced, especially by molding, which satisfied the color conditionsimposed by automobile manufacturers.

For comparison, a composite strand was produced under the sameconditions as above but modified in that the coextrusion spinning headwas replaced with a “one-component” spinning head fed by a singleextruder containing polypropylene and carbon black. The strand obtainedcontained 0.6% (control A) and 0.2% (control B) by weight of carbonblack.

A molded part was produced under the following conditions from thecomposite strand obtained.

The composite strands coming from six packages were assembled, thestrands then passing into an oven at 220° C. and then into a die heatedto the same temperature in order to form a rod which was then cooled byspraying water at room temperature (20° C.) and cut to a length of 12 mmin order to form granules. These granules were introduced into a moldingmachine in order to form a molded part.

The following table gives the characteristics of the composite strandsand of the molded parts obtained from these strands.

Composite strand Carbon Molded Glass Thermoplastic black part (%) (%)(%) Spinability Color Example 75 24.4 0.6 Good Black Control A 75 24.40.6 Poor Black Control B 75 24.8 0.2 Good Gray

For the same amount of carbon black, the invention makes it possible toobtain a composite strand having better spinability than that of ControlA, the latter giving rise to numerous breakages and an effectivecomposite strand fiberizing time not exceeding 50%. The fiberizingconditions for Control A are not acceptable from an industrialstandpoint.

The composite strand of Control B had good spinability owing to thereduced amount of carbon blacks but this was obtained to the detrimentof the color of the molded part.

1. A process for manufacturing a composite strand formed by combiningcontinuous glass filaments emanating from a bushing with continuousthermoplastic filaments emanating from at least one spinning head, thesefilaments being drawn and commingled in the form of a web into a bundleor web of glass filaments, characterized in that the thermoplasticfilaments are obtained by coextruding an organic thermoplastic in amanor amount (called the main material) with an organic thermoplasticpresent in a minor amount and containing at least one nonspinablecompound (called the secondary material).
 2. The process as claimed inclaim 1, characterized in that the coextrusion is carried out in such away that the secondary material is distributed on the surface of themain material, which serves as a core.
 3. The process as claimed inclaim 1, characterized in that the coextrusion is carried out in such away that the secondary material is included within the main material. 4.The process as claimed in one of claims 1 to 3, characterized in thatthe main material and the secondary organic thermoplastic are chosenfrom polyolefins such as polyethylene and polypropylene, polyesters suchas polyethylene terephthalate and polybutylene terephthalate, polyamidessuch as nylon-6, nylon-6,6 and nylon-12, polyphenylene sulfide andpolyurethanes.
 5. The process as claimed in one of claims 1 to 4,characterized in that the stream of the main material represents atleast 50%, preferably 70 to 95%, by weight of all of the materialsentering the spinning head.
 6. The process as claimed in one of claims 1to 5, characterized in that the weight content of nonspinablecompound(s) in the secondary material is less than 80% and preferablyvaries from 1 to 50% and better still varies from 10 to 30%.
 7. A devicefor manufacturing a composite strand formed by combining continuousglass filaments with continuous organic thermoplastic filaments, whichdevice comprises, on the one hand, at least one bushing supplied withmolten glass, the lower face of which has a very large number of holesand is associated with a coating device, and, on the other hand, atleast one spinning head supplied under pressure with molten organicthermoplastic, which includes a very large number of holes, and meansfor drawing and spraying the thermoplastic filaments for the purpose ofmingling them with glass filaments and means common to the bushing andto the spinning head for assembling and optionally winding the compositestrand, characterized in that the spinning head is suitable forcoextruding a main material with a secondary material containing atleast one nonspinable compound.
 8. The device as claimed in claim 7,characterized in that the spinning head has an internal geometryallowing the main material and the secondary material to be deliveredseparately right to the spinneret plate.
 9. A composite strand obtainedby the process as claimed in one of claims 1 to 6, the said strandcomprising thermoplastic filaments containing at least one nonspinablecompound.
 10. A product, especially in the form of a mat, woven, knit orbraid, containing at least one strand as claimed in claim
 9. 11. Acomposite having a thermoplastic matrix reinforced by glass strandsobtained from the strand as claimed in claim 9.